package com.leo.javase.nio;

import java.net.InetSocketAddress;
import java.net.ServerSocket;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.util.Iterator;
import java.util.Set;

/**
 * 
 * @author Administrator
 */
public class NIOServer {
	//标识数字
	private int flag = 0;
	//缓冲区大小
	private int block = 4096;
	//发送数据缓冲区
	private ByteBuffer sendbuffer = ByteBuffer.allocate(block);
	//接受数据缓冲区
	private ByteBuffer receivebuffer = ByteBuffer.allocate(block);
	//选择器
	private Selector selector;
	
	public NIOServer(int port) throws Exception{
		// 打开服务器套接字通道  
        ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();
        // 服务器配置为非阻塞  
        serverSocketChannel.configureBlocking(false);
        // 检索与此通道关联的服务器套接字  
        ServerSocket serverSocket = serverSocketChannel.socket();
        // 进行服务的绑定  
        serverSocket.bind(new InetSocketAddress(port));
        // 通过open()方法找到Selector  
        selector = Selector.open();
        // 注册到selector，等待连接  
        serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
        System.out.println("Server Start----8888:");
	}
	// 监听方法
	private void listen() throws Exception{
		while(true){
			// 应用Select机制轮循是否有用户感兴趣的新的网络事件发生，当没有新的网络事件发生时，此方法会阻塞，直到有新的网络事件发生为止。
            selector.select();
            // 返回此选择器的已选择键集。  
            Set<SelectionKey> selectionKeys = selector.selectedKeys();
            Iterator<SelectionKey> iterator = selectionKeys.iterator();
            System.out.println("selectionKeys size -> " + selectionKeys.size());
            while (iterator.hasNext()) {
                SelectionKey selectionKey = iterator.next();
                iterator.remove();
                handleKey(selectionKey);
            }
		}
	}
	//处理请求
	private void handleKey(SelectionKey selectionKey)throws Exception{
		// 接受请求  
        ServerSocketChannel server = null;
        SocketChannel client = null;
        String receiveText;
        String sendText;
        int count = 0;
        // 测试此键的通道是否已准备好接受新的套接字连接。  
        if (selectionKey.isAcceptable()) {
            System.out.println("------------- isAcceptable");
            // 返回为之创建此键的通道。  
            server = (ServerSocketChannel) selectionKey.channel();
            // 接受到此通道套接字的连接。  
            // 此方法返回的套接字通道（如果有）将处于阻塞模式。  
            client = server.accept();
            // 配置为非阻塞  
            client.configureBlocking(false);
            // 注册到selector，等待连接  
            client.register(selector, SelectionKey.OP_READ);
        }
        else if (selectionKey.isReadable()) {
            System.out.println("------------- isReadable");
            // 返回为之创建此键的通道。  
            client = (SocketChannel) selectionKey.channel();
            //将缓冲区清空以备下次读取  
            receivebuffer.clear();
            //读取服务器发送来的数据到缓冲区中  
            count = client.read(receivebuffer);
            if (count > 0) {
                receiveText = new String(receivebuffer.array(), 0, count);
                System.out.println("服务器端接受客户端数据--:" + receiveText);
                client.register(selector, SelectionKey.OP_WRITE);
            }
        }
        else if (selectionKey.isWritable()) {
            System.out.println("------------- isWritable");
            //将缓冲区清空以备下次写入  
            sendbuffer.clear();
            // 返回为之创建此键的通道。  
            client = (SocketChannel) selectionKey.channel();
            sendText = "message from server--" + flag++;
            //向缓冲区中输入数据  
            sendbuffer.put(sendText.getBytes());
            //将缓冲区各标志复位,因为向里面put了数据标志被改变要想从中读取数据发向服务器,就要复位  
            sendbuffer.flip();
            //输出到通道  
            client.write(sendbuffer);
            System.out.println("服务器端向客户端发送数据--：" + sendText);
            client.register(selector, SelectionKey.OP_READ);
        }
	}
	
	public static void main(String[] args) throws Exception {
        int port = 8888;
        NIOServer server = new NIOServer(port);
        server.listen();
    }
}
